A Systematic Investigation on Fouling of NF and RO Membranes by Complex Suspensions Containing Colloids and Dissolved Organic Macromolecules

摘要含胶体和溶解有机大分子的复合悬浮液对纳滤膜和反渗透膜的污染进行了系统的研究世界范围的水资源短缺使得使用纳滤和反渗透(RO)的非传统来源生产饮用水成为一种有吸引力的饮用水供应选择。然而，目前应用于此目的的纳滤和反渗透在经济上效率低下，这主要归因于膜材料的污染。改进需要阐明污染机理和膜性能的预测模型。虽然已经对膜污染进行了大量的研究，但几乎所有的机理研究都集中在单一的污染类型上。这些研究的结果不适用于水和废水应用，因为在这些系统中，污垢总是由胶体材料和溶解的有机大分子引起的，它们之间的相互作用可以显著改变彼此的行为。因此，对含胶体和溶解有机大分子的复合悬浮液在纳滤膜和反渗透系统中的行为进行系统的研究对于进一步发展这类水和废水处理技术是非常必要的。本项目的总体目标是确定和定量描述胶体-大分子相互作用对含胶体和溶解有机大分子的复合悬浮液对纳滤膜和反渗透膜污染的影响。该研究计划基于三个假设：1)胶体与大分子之间的相互作用阻碍了浓差极化层中彼此的反向传输；2)溶解有机大分子的存在改变了胶体的表面性质，导致胶体相互作用的改变，从而改变了污垢层的性质；3)颗粒的传输和污垢层的形成受两个耦合的物理化学过程控制：浓差极化和颗粒附着。本项目将采用系统的理论和实验方法来量化重要的污物-污物和污物-膜相互作用对膜污染的三个关键方面的影响：1)污物的回输；2)膜表面的污物沉积；3)污染层的形态和水力阻力。这些相互作用将在纳米尺度上用原子力显微镜在各种溶液条件下进行测量。新的理论将根据测量的相互作用势确定相互作用的污染物的后扩散系数和沉积速率，并将这些相互作用定量地纳入污染物运移模型和膜通量模型。拟议的研究旨在改进现有的可持续供水技术，这对全球水资源问题具有深远的影响。它有很强的教育成分。两名研究生和一批本科生将通过该项目获得研究性培训。学生报告将在国家科学会议上发表。膜过滤实验系统将被纳入研究生水平课程的实验室课程。为了接触到更多的人群，这项研究将通过暑期科学学院项目、新生迎新课程和关于纳米技术和可持续发展的公共研讨会系列向高中生、大一本科生和当地社区介绍。

ABSTRACTA Systematic Investigation on Fouling of NF and RO Membranes by Complex Suspensions Containing Colloids and Dissolved Organic MacromoleculesThe world-wide water shortage has made drinking water production from non-traditional sourcesusing nanofiltration (NF) and reverse osmosis (RO) an attractive option of potable water supplies.However, current applications of NF and RO for this purpose are economically inefficient, largely attributed to the fouling of membrane materials. Improvement requires elucidation of fouling mechanisms and predictive models for membrane performance. Although considerable research has been done on membrane fouling, almost all mechanistic studies have focused on a single foulant type. Results from these studies are not applicable to water and wastewater applications because fouling in these systems is always caused by both colloidal materials and dissolved organic macromolecules, the interactions between which can significantly alter the behavior of each other. Therefore, a systematic investigation on the behavior of complex suspensions containing colloids and dissolved organic macromolecules in NF and RO systems is imperative to further development of these technologies for water and wastewater applications.The overall project objective is to determine and quantitatively describe the effects of colloid-macromolecule interactions on fouling of NF and RO membranes by complex suspensions containing colloids and dissolved organic macromolecules. The research plan is based on three hypotheses: 1) The interactions between colloids and macromolecules hinder the back transport of each other in the concentration polarization layer; 2) The presence of dissolved organic macromolecules changes the surface properties of the colloids, leading to changes in colloidal interactions and consequently fouling layer properties; 3) The particle transport and fouling layer formation are governed by two coupled physical chemical processes: concentration polarization and particle adhesion. This project will take systematic theoretical and experimental approaches to quantify the effects of important foulant-foulant and foulant-membrane interactions on three key aspects of membrane fouling: 1) foulant back transport; 2) foulant deposition on the membrane surface; and 3) morphology and hydraulic resistance of the fouling layer. These interactions will be measured at nanoscale with atomic force microscopy under various solution conditions. New theories will be developed to determine the back diffusion coefficient and deposition rate of interacting foulants based on the measured interaction potentials, and to quantitatively incorporate these interactions into a foulant transport model and a membrane flux model.The proposed research aims at improving current technologies for sustainable water supply, which has profound broader impacts on global water resource issues. It has a strong educational component. Two graduate students and a number of undergraduate students will obtain research training through the project. Student presentations will be made at national scientific meetings. The membrane filtration experimental system will be incorporated into the laboratory sessions of a graduate level course. To reach a larger population, the research will be introduced to high school students, freshman undergraduate students, and the local community through the Summer Science Academy Program, the freshman orientation class, and a public seminar series on Nanotechnology and Sustainability.